How to make automatic focus of tagfield on some condition

I have a tagfield in which I am loading some value and sending to the server. What I want is when reload that tagfield component again, those value should be automatically selected. currently They are not automatically selected, But If I am giving a focus to the tagfield then those value are coming as selected.

What is the way to give automatically focus on some condition. Not all the time.

Right now I am just displaying the data but this is not correct way to do and in IE this is not working.

Here what I am doing currently

if(myField.xtype == "tagfield"){
        myField.xtype.setValue(myValue);
        myField.xtype.inputEl.set({'placeholder':myValue});
    }

What I want is

if(myField.xtype == "tagfield"){
        // Automatic Focus  OR
        // Someway by which I can set the value
    }